The raid instance is supposed to be 4 times the size of Obsidian Sanctum, roughly the size of Alterac Valley

All the bosses will have new models

Ground mounts will be allowed.

The first four bosses will be non-linear before you get to the final three that are in a linear fashion, with Ragnaros at the end.

Ragnaros will be the final boss. It will NOT be an heroic-only encounter like Sinestra but the heroic version will be completely different from the normal one and developers wanted to make sure it feels really unique and pretty hardcore.

There will be more bars/meters to make it easier to watch certain mechanics in contrast to a simple debuff stacking

You won't need fire resistance and bosses won't have any either.

There will be epic recipies drops for all the usual professions.

Tier 12 Armor Sets

All T12 sets will be fire themed (duh)

Not new but reminder: Warlock will be themed after those awesome looking fire spiders

One plate set will be themed after the new fire giants (Anthricyst maybe?), the shoulders will be like the fire giant's face.

Set bonus will be firelands themed too and may resemble certain boss abilities

Raid Misc.

There will be a new Baradin Hold boss - another loot pinata (his words!)

The interviewer also asked for a second raid dungeon, Cory ignored that part and only answered the Baradin Hold part - interpret yourself.

Legendary:

The proc of the weapon will be offensive and not suited for healers

Weapon will be forged in major cities (Stormwind and Orgrimmar respectively)

There will be a 'very long' event with a lot of voice acting and the Blue Dragonflight.

Your guild will get a reward if you complete the achievement for the Legendary staff. It will most likely be a pet, it will have an unique look (not necessarily fiery) and a "legendary" feel.

Both 10 & 25 are supposed to get the weapon roughly at the same pace

25M will have s small advantage of getting the profession related parts done quicker

Nothing more on what profession related parts of the legendary are but it will be only a minor part of the progression to the legendary, focus is on raiding.

Encounter Journal (i.e. boss guides):

Will be on PTR

Will not require unlocking by killing the boss or something

They start with entries for Cataclysm content only but plan to add WotLK, TBC and vanilla entries too - later

There will be no loot wishlist but they have plans for that. Loot will be listed for encounters and sorted by difficulty.

Quests:

There will be a new epic level 85 questline around Thrall

It's not revealed if that is about Thrall (maybe) becoming the new aspect of earth

No epics as reward, story is the reward

This new questline can be completed entirely in solo.

New Daily quests will be "modular" i.e. you start with a base set of quests and earn a currency as reward. With this currency you can unlock other quest hubs and decide how you unlock all of the dailies. This will be acompanied by heavy phasing.

Phasing will only change the area, you will still be able to play with your friends even if they have progressed further